This invention relates generally to gas samplers, and more particularly to sampling cartridges for collecting and detecting particulate in a gas.
Conventional gas samplers for collecting particulate include a housing having a vacuum pump for drawing gas past a collector such as a filter paper, a glass fiber filter media, a filter cassette or an activated carbon cartridge.
Limitations with such conventional gas samplers for collecting particulate include the vacuum pump generally producing a low flow rate of gas to be sampled, the filter becoming clogged, and the vacuum pump being noisy.
A high-flow rate, low-noise, gas sampling apparatus which overcomes the above limitations and may be used for collecting particulates such as biological, chemical, and radioactive material from a gas on a collector such as an impaction collector is disclosed in commonly assigned U.S. patent application Ser. No. 10/177,749. This sampler includes a housing having an inlet and an outlet, and a fan disposed within the housing for drawing the gas into the inlet, past the collector for sampling, and exhausting the gas through the outlet. The sample collector preferably comprises a foam or porous cloth material of the type described in U.S. Pat. No. 6,435,043, entitled xe2x80x9cImpaction Substrate and Methods of Usexe2x80x9d, the entire contents of which is incorporated by reference herein. The fan is operable to produce a flow of gas through the housing of greater than about 50 liters per minute, and preferably greater than about 200 liters per minute, with a noise level emitted from the apparatus of less than about 60 decibels. The sampler may be configured as a compact, unobtrusive, portable, light-weight apparatus for use in various indoor or outdoor locations. It may also include a sensor for the detection of radioactive material collected on the collector, and a processor for monitoring the sampling, and may be linked to a communications network such as the internet. Related methods for collecting particulate from a gas are also described in the referenced patent application.
There is a need to further ensure the integrity of collected particulate samples.
The present invention provides, in a first aspect, a sampling cartridge for a gas sampling apparatus. The cartridge includes a shell having a cylindrical wall and a sampling window extending through the wall. A spool is positioned adjacent the shell and has a sample collector located at a first circumferential location and a window closing surface located at a second different circumferential location. The spool and shell are rotatable relative to each other such that the sample collector and window closing surface can be selectively alternatively positioned adjacent the window for sample collection and cartridge sealing respectively. The self-sealing feature protects the collected particulate sample during cartridge removal, handling and transport.
The spool is preferably coaxial with and internal to the shell. The shell may be at least partially transparent to permit visual confirmation of previous use.
The spool may have a plurality of sample collectors at circumferentially spaced locations to permit sampling at different time intervals. Each of the sample collectors may comprise a foam or porous cloth material. The sample collector may preferably comprise a perforated foam material.
The cartridge may further include a fully encapsulated segment of the sample collector material as a negative control. The cartridge may also include memory means for storing chain of custody information about the cartridge. The chain of custody information can include personal identification information of a cartridge replenisher. Preferably, the memory means comprises a radio frequency tag which is serialized for traceability and write-protected to ensure single use of the cartridge.
The cartridge can further include a duration sample collector exposed through the window and separate from the spool. The duration sample collector may be mounted at a first circumferential location on a second spool which is independently rotatable relative to said shell. The second spool may include a second window closing surface at a second circumferential position. The first and second window closing surfaces may be automatically positioned adjacent the window whenever the cartridge is removed from the gas sampling apparatus.
The sampling cartridge may be combined with gas sampling apparatus having an access door. Preferably the cartridge is automatically sealed by positioning the window closing surface(s) adjacent the window, whenever the access door is opened. The gas sampling apparatus may further include a mandrel for mounting the cartridge and producing relative rotation between the shell and the spool(s).
The present invention provides, in a second aspect, a sampling cartridge for gas sampling apparatus which includes a cylindrical shell having a sampling window, and a pair of internal self-sealing sample substrate spools. Preferably, the shell is transparent and includes a radio frequency tag for storing chain of custody information relating to the cartridge. The chain of custody information may include personal identification information of a cartridge replenisher.
The cartridge may further include a fully encapsulated portion of virgin sample collector substrate material. The first spool may include multiple circumferentially spaced interval sample substrates while the second spool may include a single duration sample substrate. Each spool may further include a window closing surface. The first and second spools are independently rotatable relative to the shell, and each spool is self-sealed by rotating its window closing surface into alignment with the window.
The present invention provides, in a third aspect, a method of collecting a particulate sample with gas sampling apparatus having an access door. The method includes collecting the sample on a substrate, automatically sealing the substrate whenever the access door is opened, and recording chain of custody information on memory means associated with the substrate. The collection step may comprise collecting the sample on a substrate of a sampling cartridge. The sealing step may comprise self-sealing the cartridge. The recording step may comprise recording the chain of custody information for the cartridge on a radio frequency tag integral with the cartridge. The chain of custody information may include personal identification information of a cartridge replenisher. Further, the cartridge may incorporate a fully encapsulated portion of virgin substrate material as a negative control.
The present invention assures the integrity of collected particulate samples by employing a self-sealing sampling cartridge, automating the sealing of the cartridge upon opening of the access door of the gas sampling apparatus, incorporating a fully encapsulated portion of the virgin substrate material as a negative control, and storing chain of custody information on a Radio Frequency (RF) tag integral with the cartridge. These and other features, advantages and objects of the present invention will be more fully understood from the following detailed description of preferred embodiments.